An image pickup device, for instance a still-picture camera or a video camera, has an image sensor, which generates an electrical signal (image signal) describing the light impinging on the image sensor, i.e. an image of the scene facing the image sensor.
The image sensor is fed by a pulse pattern generator, which generates driving signals (operating voltages and various clocks) needed for operation of the image sensor.
Before being processed, the image signal generated by the image sensor is amplified at a gain, which is directly or indirectly selected by the user of the image receiver through adjusting means.
Image sensors are generally designed to handle overexposure, up to a value called maximum charge handling capacity Qmax, for instance 400%. At high gain settings, this overexposure capability leads to huge values (at 12 dB, 1 600%) of the amplified signal, thereby generating unacceptable ringing and streaking. Furthermore, high gain also implies more noise in the amplified signal.